The performance of a device, in particular an engine, may be monitored in order to detect a deterioration and/or predict a failure of the device. Such methods may be applied to engines, for example a gas turbine engine and in particular a jet engine, for which reliability is very important. In the case of a jet engine, there are presently two main methods for monitoring the performance of the engine.
The first of these monitoring methods comprises manually recording a steady-state snapshot during the take-off sequence of an aircraft. The pilot runs the engines up to their maximum and allows them to settle for a fixed period whereupon the values of the key engine parameters are noted and checked against datum values. If the values of the key engine parameters are within acceptable limits of the datum values the pilot will continue with the take-off run. The datum values comprises the parameters when the engine was initially installed or at a periodic engine check. Once the pilot has completed his flight he reports the values of the engine parameters and these are entered into a tool, which outputs a trend of the engine parameters and therefore engine performance from flight to flight. This tool is used to identify engines that have lost a certain amount of performance.
The second of these monitoring methods comprises a snapshot capturing system on board the aircraft. The system works during a flight and captures a snapshot based on a set of criteria, which the relevant parameters lie within. The system records a number of snapshots during a flight. The system rates the snapshots taken according to a desired set of operating parameters and the length of time the engine spends within a range of these parameters. Once the memory has been filled, if the next snapshot has a higher rating than the snapshots stored, then the system will remove the lowest rated snapshot and place the new snapshot within its memory.
There are however a number of problems with the above-described methods. In the first method, the snapshot system is susceptible to a human error with the pilot involved in noting down the values of the parameters. Also, the degree of accuracy at which the values can be taken from the dials is also limited. Furthermore, the snapshot system of the first method only looks at the performance of the engine at one flight condition. The accuracy of the trend produced by one point per flight is also limited and the validity of the trend relies on the accuracy at which the pilot can record the information during the take-off sequence.
In the case of the second method, having set criteria where the plane has to be operating for a snapshot to be taken prevents the engineer from understanding the performance of the engine across the whole flight profile.
The present invention therefore seeks to address these issues.